Geophysical method and apparatus



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GEOPHYSICAL METHOD AND APPARATUS Filed May 15, 1928 7 Sheets-Sheet 1 a mnubo'c Harvey C. Hayes 351 Gum;

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v GEOPHYSICAL METHOD AND APPARATUS Filed May 15, 1928 7 Sheets-Sheet 7 awuamtoz f/wvey Q Hayes 061 C1 flown-@1 1 Patented July l4, 1931 UNITED srAr-Es PATENT orrics HARVEY G. HAYES, OF WASHINGTON, DISTRICT OF COLUMBIA GEOPHYSICAL METHOD AND APPARATUS Application filed May 15, 1928. Serial No. 277,966. 7

' (GRANTED UNDER THE ACT OF MARCH 3, 1883, 'AS AMENDED APB-H1 30, 1923; 370 0. G. 757) During comparatively recent years, efiorts with improvements in methods and ap arahave been made by parties interested in subtus depending upon these peculiar e astic' terranean deposits of various kinds to de-; qualities of various types of earthstructermine' the nature of the" earthls surface ture. It is contemplated by the present in-' 5 over large sections of land without the nevention to simplify the exploration work of 5 cessity of drilling test holes, as has hereto this character in such a way that it may fore been the universal practice. Much'time be more rapidly carried on with greater'- I 1 and money has been spent in the past by pro assurance of accuracy in theresults obtained a t ducers of oil, as well as those interested in and with the recording of a maximum 1 other subterranean deposits, in the drilling amount of information regarding the 'char- 5 of test holes which frequently bore no reactor of the earths surface through" whichi sults, This old time procedure is very slow, the vibrations-have travelled. With these and due to the need of drilling to such great and other incidental objects in vietsfl'such depths has entailed considerable expense, all as Wlll become more apparent as the; detailed 1 basexl on the bare possibility and not upon description progresses, a preferred form of '5 certainty of locating some valuable deposits.., embodiment of the invention will now be Of course, prlor to the drilling of such test described in detail with reference to the v holes, it was the common practice to employ accompanying drawings in WlllChexpert geologists to study surface conditions, Figure 1 ma diagrammatic view showing '20 which, together with available data of the the general arrangement of sending and re- 70 section being explored, might serve .to indicelving StiltlOlS employing the improved cate the likelihood of the existence of the demethods and p aratus. sired deposits, but such methods, for obvious g 2 is g -m ew i g reasons, are not fully satisfactory. It. is g e r d il of the instruments employed frequently .the case that a large pool of oil, t the sending station. 75 f le, may b lo t d b th th Figure 3 is a diagrammatic view showing earths surface at a point where no i diom of the instruments employed at a receiving tion of its existence is given at the surface. ion. p

For this reason, the practice has become F1gure4 is a sectional view of one of the more and more prevalent to study the geot c rs employed. H physical characteristics of the earths sur- F 1g111'e'5 is a perspective view of the face over large areas. It is well known, for r q ompass and transit as set up to de-- example, that. a frequently encountered geo- 1 3 6 a e mglogical structure that is suitable for the acg e 6 1S a lan View ofthe oscillograph cumulation of oil is a salt dome which has and unmg for control. 85 certain peculiarities with respectto density Figure 7 is an elevational view of the l and elasticity, as well as certain peculiar oscillograph. I p magnetic qualities. Working upon the basis Figure 8 is a wiring'diagram of the oscilof the differences in density of various geolo aph and related elements. 4o logical strata, vast areas have been explored V igure *9 is a detail of a section of the so by means of torsion balances or similar dephotographic record. vices which give an accurate determination Figure ,lOis a detail of the wheel for of the relative values of the earths gravitaforming time lines.

v the different earth formations, have resorted Referring now to Figure 1 the invention to means for setting up vibrations at selected contemplates the creation of. vibrations simoints andv "detecting these vibrations at ilar to sound waves by any suitable means other points within -a range of a fewmiles. as by setting ofi an exflosive charge at a "50 v The present invention has to do primarily point which hasbeen esignated O. This tional pull at various points. Others, de- Figure 11 is a side view of the holder for pending more upon the elastic qualities of the oscillograph strings.'. Y 05 .inches in diameter, which may be drilled by any suitable means. In determining the depth at which the explosive charge shall be set oil", the important factor is the prevention of loss in the power' of the, charge through the undue blowing out of an opening immediately above the charge. Gompressional waves similar to sound waves but probably of a frequency below the range of audibility, will be set up upon the explosion of the charge and will radiate in all directions. Obviously it will be advantageous to retain as much as possible of this vibrational energy within the earth itself and to prevent its escape into the free air above the charge.

At a point designated A, which is near the point of explosion, preferably about 1,000 feet from the latter, the equipment constituting what will be termed the sending station, is set up, while at points B, C, and

which are at a greater distance, preferably 4 or 5 miles from the source of explosion, the apparatus comprising the several receiving stations will be set up. These receiving stations may be located in any suitable manner with respect to each other, but preferably will be located substantially along a straight line and at a distance of 1 to 1 miles apart. While three receiving stations have been illustrated in Figure 1, it will be obvious that a greater or less number may be employed, one station being sufficient if esired, while a greater number than three is preferable in order to take readings over as much of the territory aifected by the charge as possible. If suflicient equipment were available, it would be desirable to arrange a complete series of stations, either in a circle about the point of explosion or along the four sides of a square; having the point of explosion at its center. Substantialliy the same equipment is required at all of t e stations, receiving stations, and while some diiferences exist between the sending and receiving outfits, it is desirable to equip all of the sialtions alike to render them interchange a e.

Considering how the equipment at the several stations, each is provided with a radio compass 1, which includes a balanced loop receiver and any suitable form 'of sensitive radio receiving apparatus. A radio transmitter 2 is also provided at each station together with a radio receiver 3, which,

among other things, may be used for interincluding the sending and communication between the stations. Two vibration or sound detectors designated 4 and 5, which are preferably of magnetoelectric construction, and which will hereinafter be termed terraphones, are provided at each of the stations, and these are adapted to be suitably connected to the input terminals of vacuum tube amplifiers 6 and 7 respectively. From the output terminals of these amplifiers, suitable connections are provided to the terminals of an oscillograph 8. This instrument, as contemplated by the present invention, is provided with" two strings, one of which is related to each of the terraphones to control the photographic rccording of the vibrations reaching.

the terraphones. Other accessory equipment is also provided at each of the stations and will be mentioned hereinafter in connection with the explanation which will now be given of the preferred "method of operation. Having adopted a suitable location for the point of explosion O, and having selected desirable locations for the several stations by merely estimating the desired distance-s, radio compasses for each of the stations will be set up at the selected points which may be designated a, 6, c, and d.

Antenna equipment 9, rovided for" each of'the stations. will also e located at substantially the same points, except that the antenna for station A will be first located at 0, so that signals may be sent out from each station and received by the radio compasses of all of the others. For example, at the sending station the switch 10 will be thrown to the left in Figure 2 in order to place the antenna 9 in the circuit of the radio transmitter. The terminals 11 of the radio transmitter are constantly in circuit with one arm of a switch 12,- and a radio signalling key 13, so that upon each depression of this key an impulse or signal will be sent out from the antenna 9 of the sending station which at this time is located at the point of explosion as indicated in dotted outline. In practice, a series of such signals will be sent out during the course of which all of the radio compasses at the points a, b, c, and 03, will be adjusted until the loops 101 are directed toward the source of the signal. Preferably, as shown in Figure 5, a transit 102 will be employed in conjunction with eachradio compass, so that not only the relative direction to the point of explosion maybe determined but the precise direction with respect to magnetic north may also be ascertained. For this purpose the transit may first be sighted upon any suitable pair of points on the loop of the compass such as a pair of hair lines 103 formed on pieces of glass mounted on the loop preferably to form a sight line at right angles to the latter.. The reading with the old. If desired, the scale 104 tached to the loop may be 109 to the same reading as in degrees of a scale 104 secured to the loop, with respect to a fixed mark 105 may then be noted and compared with the reading of a similar scale 106 movable with the telescope 107 of the transit relative to the compass needle 1.08. A comparison of these readings will determine the position of the loofp with relation to magnetic north at I that time and its position after subsequent adjustment to locate the source ofsignal may bedefinitely determined by comparison of thenew reading of the compass scale atmade admstable \thereon so that after a bearing has been taken by the transit the compass scale may be adjusted and set by means of a screw the transit scale.

In any; position of the loop so lon as the position of the main body of the ra io com ass 1 is not disturbed, the bearing with relation to magnetic north mayithen be d1- the transit if desired an the terra'phones what greater distance apart with its radio compass at from its scale. aving thus rectly read the radio compass'bearings indetermined fdicated by the lines 14 in the drawings, a line perpendicular each of the stations,

to the bearing line at may be determined by swinging the loop throu h 90 and using at a given .dis-

'tance, which is preferably 250 feet, to each side of the point from which the bearing was taken, one of the terraphones may be inserted into the ground.v This will insure the location of the terraphones at a distance ofsay 500 feet part,v and along a line at right angles to and bisected by the compass bearin'g previously: determined.

If desired, each of the stations B, C, and D, may send out radio signals by means of its transmitting apparatus through antenna equipment located at the same points c, and d, at which the radio compasses were located. At this time, all of the remainin stations, including; the sending station the point a, may take vup their bearings by asses with respect to the transmitting station. It'is only necessary or important that one of the receiving stations be em.- ployed in this way to send out signals, although if desired, eachstation may successively send out sign the compasses of a check upon the original determinations made. It may be found desirable to locate for station A at a somethan those for 1,000 feet, al-

the remaimng stations, say

In thIS way,

though this is not essential.

the terraphones for the sending station would form substantially an equilateral triangle with the point 0. It will apparent -that the method outlined will resalt in the determinationof all of the angles between the several stations,

with some degree of accurac render. it easily" point to another.

' charge of the explosive,

means of their -rate-as wil als to be picked up by, the remaining stations as.

depressed.

so :that if one of the distances is known or determined remaining distances may be etermined by triangulation. For example,'.the distance from the point 0 to the pointa, may be accuratel measured so that with the an les determined in the way indicated, all ot er distances may be computed, or it'may be found simpler to determine tween two of the points b and 0, am 1e, of the receiving stations.

l of theequipment for each station, will preferably be mounted on an automobile or other means of conveyance, so as to transportable from one This will provide an easy method, furthermore, of determining the distance between stat ons since the odometer reading may probably be taken with sufficient accuracy for this purpose.- be borne in mind that accuracy within one or two per cent location of desired deposits from a known point will be sufficient for the purposes, although, of course, greater accuracy if obtainable is desirable.

Having thus determined the positions of the several stations, and having connected the instruments in the manner shown, as well as having buried the explosive charge in the manner hereinbefore indicated, all is substantially ready for the firing of the" explosive and the making of the records which will indicate not only the speed of travel 'of the compressional waves set up but other characteristics as well. Prior to the disradio communication' between the stations will determine whether or not all are prepared to take the necessary records. As soon as the sending station has ascertained that all of the remaining stations are prepared, several warning signa will be sent out from the radio transmitter at station A, followed by a signal advising all of the stations to set the. oscillographs into operation; This will normally involve the closing of certain electrical circuits and the starting up of the camera mechanism which is adapted to feed a photographic record strip at a uniform -be more fully explained herein- If desired,'the oscillograph may already be' in o 'eration except for the movement of the lm so that the signal may be employed to bring about merely the starting of thecamera. Within a fraction of a second, the switch 15 at the sending station will be closed. At the instant of closing this switch a signal will be sent out by mean: of the radiotransmitter 2 in precisely thl same manner as if the radio key 13 had beei This is' due to the closing 0 the signal circuit by meansof the branch 1! of the switch. All of the radio receivers. at all ofrthe stations, except the sendin after.

all of the Itisto the distance be- 1 in the determination of the r station, will pick up this signal and by means of the relays 16, whose armatures are operated upon receipt of the signal, will pass it along to one of the strings of the galvanometers forming a part of the oscillographs. For this purpose there is in the relay circuit a battery 17 and a variable resistance 18, together with a primary winding.19 of an induction coil. The resistance 18 may be adjusted to any suitable value in order to produce the desired magnitude of effect upon the galvanometer. A secondary winding 20 of the induction coil is placed in the line from one of the terminals of a terraphone amplifier to one of the strings of the galvanometer and in order to protect the latter still further, a variable resistance 21 is also placed in parallel with this secondary described,'therefore, a record is produced on the hotographic film at each of the stations B, and D, indicating the precise moment at which the switch 15 was closed. The corresponding record -at station A, must be formed in a slightly different way since at this time the switch at this station must place the transmitter rather than the receiver in the antenna circuit. A means for providing the desired record at station A will now be described;

Another circuit which is completed upon the closing of the switch 15, is that which serves to set off the explosive charge. This circuit includes a battery 22 and suitable leads to the explosive charge, and from the latter to the Variable resistance 18. Another connection from this resistance completes the circuit to the switch 15. At the sending or central station furthermore, the circuit will be closed through the terminals 23, as by the placing of a shunt directly across the latter, so that the circuit through the point of explosion will be divided at these terminals, a portion of the current being passed through the primary winding 19 and battery 17. It is this portion of the current which will produce a disturbance inthe secondary winding 20 upon closing of the switch to provide a record of such closing. It will be apparent that the explosion will not occur at' the instant of closing the switch 15, but a short interval of time is required for the "electric current to set off the charge. \Vhen the explosion actually occurs, the circuit from the battery 22 will be broken and a sudden kickback will take place through the resistance 18 and coil 19, which will roduce another record at station A throng the secondary winding upon the same string of the galvanometer as previously affected. The time period between the first mark closing of switch 15 and the actual time of explosion may thus be accurately determined by means of the time marks which, as will be later more fully described, may be made at winding. By the means just indicating the.

intervals of 1/100th of a second u on the hotographic record of the oscil ograph.'

hile the period will be directly indicated only at station A, the correction thus determined may be applied to the record of the closing of the switch at the remaining stations as well.

Upon.the exploding of the charge at the point 0, a series of compressional waves will be sent out through the surrounding earth in all directions, and these will travel by various courses to the terraphones at the several stations. Some of these waves may travel in a direct line through the upper surface soil of the earth, while others may, in advancing also, travel downwardly to a certain extent until they strike a subterranean mass of different density and elastic qual ities than the surface soil. For example, in regions favorable to the accumulation of oil, there will frequently be encountered large salt domes which are of less density than t the upper surface soil but which are of considerably greater elasticity than the average surface soil. Assuming that a salt dome is located in the position indicated by the outline designated 24 in Figure l, certain of the compressional waves will pass downwardly from the source 0 to the more elastic medium where they will be refracted and through which they will pass at a velocity of four or five times that through the upper surface. After passing for a considerable distance throughsuch a salt dome, the waves will emerge and be again refracted so that they may pass directly through the remaining soil to one of the terraphones at the station B, for example. If the portion of the path of the waves which extends through the more elastic medium 24 is sufliciently great with relation to the total path, these refracted waves may reach the terraphone prior to the direct Waves which travel only througlrthe surface soil. There will furthermore be a distinct difference in the amplitude and general form of these waves as reproduced upon the oscillograph record. Still other waves may strike the mass 24 at such an angle as to be reflected from its surface rather than passing into the more elastic medium and being refracted thereby. Instances of this type are illustrated by waves reaching both of the terraphones conneeted with the station trates diagrammatically the course which such reflected waves might follow upon striking and rebounding from the surface of the salt dome. Waves of this character are readily distinguishable on the records produced, from waves which have either travelled directly through the surface soil or have been refracted.

From the diagrammatic showing in Figures 1, 2, and 3, it is believed to be clear ust how each terraphone upon receipt of A. Figure 1 illus-- .40 phone may be a wave will convert it into an electricalimpulse which may be amplified by the vacuum tube amplifier 6 or and then sent to one of the two strings o the galvanometer forming a part of the oscillograph. Any suitable type .of detector may be employed for the purpose of the conversion mentioned,

although a construction-of the'general type shown in Figure 4 is deemed preferable.

be termed a terra- This device which may phone comprises a conical casing in'thethroughthem two south and two, northbe-establi'shed, like poles being.

The armature is poles will opposite each other.

mounted on a rod 28 which extends from the tip of the cone, the construction being such that relative movement is permitted between the cross and the laminated ring 26.. It will beapparent that when a compressional wave :reaches the casing 25, the latter will be vibrated but the armature, due to its inertia, will tend to remain st tionary; This will vary I the flux in the magnetic fields set -up by thecoils 271 and will bring. about a variation in thecurrent flowing throng these coils. By connecting thecoils in the appropriate manner with primary o a transformer system, which may form a part oithe -amplifier units 6 and 7 the comb ned variations in all of the coils of a terraamplified and sent through the galvanometer. strin tails as to this type 0 mayxbe .had to my copending application .s. .221,520 filed September 23, 1927.- 45, e The two records produced by means 0 the two ,terraphones 4 andt, close prox imity upon the photographic, stripof' the osclllqgra h, will not only upon eac other, but

will have l ferences in their characteristics which will the course.

' that the beam. of 11 f1 f0 used upon the fi m passing the opemng aid materially in interpreting which the emitted waves haveffollowed.-

After a lapse of a sulficient period- 0 time which will be a matter offseconda'orof hght,'w ch 1s of relatively flat but nude 1 formation,', a pair ofvgalvanometer strings 5 such time as may waves which it is desired to recordto trave to the several stations, preferably be sent out from the sending station by means of the radio key 13 and upon be required for all of the 0 receipt of this signal, the oscillographs an other apparatus at all of the stations may be shut down simultaneously. This procedure willinnd to produce uniformity in results at all of the stations, and will also Ila-bring about -a saving of trans- A brief description required 1s ,For further d e--- detector reference f 35 secured to thetube: 34 preferably be s d f carried within the tube 35 and the latter together with the tube 34 is adjustable to observeas. alcheck v d is slidable in grooves of the film on which i the records are The final on the record. Between the contacts 23 at the several. stations theremay be inserted a radio key which may be operatedat any time to make notation on the related records. Thus eachtime a new record roll is inserted, it may be markedwith the station symbol by the use of such a key. It will be apparcutthat a comparison of the records from allof the stations, particularly with regard to the differences in the times of travel of the various waves, will provide means for not only indicating the general location of a subterranean deposit, such as a salt dome, but will even serve to give a general indication as to its contour.

will nowbe given of recording apparatus one suitable form of or oscillograph.

Referring particularly to Figures 6, 7, 10 and 11, it will be noted that a camera '30 is provided and this may be of any suitable 9o construction along the lines of a small moving-picture camera with constant uniform feed of the fihn in place of the usual inter-- mittent feed in such cameras, All that is suitable mechanism for feeding the record film from a supply roller past 'a narrow slit toward the front of the camera and onto-a storage roller. A spring motor.

h 31 may form a part of the camera for-the a the film feeding devices. The narroworizontal slit' may be formed in a disc or diaphragm at the rear of a tubular passage 32. A beam of light may be 'formedby'means of a small electric lamp 33 which is suitably mounted within atube 34. Within this tube there will also be provided suitable condensing lenses I which will tend concentrate V the rays of light fro 'Kthesource 33. A smallemtube purpose of operatin passed throughanbpenlng 1n thepole pieces 36 of 'an electromagnet which is ener-. by a coil 37. Additional lenses are taina proper focus. It will be understood ht thus created will be In'the path of this beam- 32 of the camera.

will beheld-in a'vertical plane so that each string will cast a oint shadow upon. the record filin. 'For t is urpose a holder 38 ormed in blocks 39 secured. to the pole pieces of the magnet and this holder, as bestshown in Figure 11,

carries the two strings 40. Suitable conductors are provided on the holder for con-.

necting the ends of each string to a pair of ,6 pairs of contacts 400.

i0 vibration.

the base, of the holder and when the latter is inserted, as shown in Figure 7, a pair of contact springs 401 on each side of the holder will engage one of the In Figure 7 there is shown only one pair of spring contacts 401, which engage the lowermost pair of contacts on the holder 38 and are in turn connected to sockets 402 on the base plate of the instrument. It will be understood that a similar arrangement on the opposite side serves to connect the upper pair 0 -contacts 400 with suitable binding posts or sockets 403 mounted in the base of the oscillograph. The ends of the strings 40 are thus connected to suitable terminals which in'turn are connected to the terraphone amplifiers in the manner indicated in Figures 2 and 3. It will be apparent that the strings 40 form an obstruction in the path of the beam of light so that as the photographic strip is moved past the opening 38 a pair of lines unaffected by light will be formed thereon and these will be displayed as white on black in the developed record. lVhen an electrical impulse is imposed upon the strings 40 by means of the terraphones or the radio apparatus they will vibrate and those portions which are in the path of the beam of light will produce a wave line upon the record corresponding to the impulse received. In addition to the record of the movement of the strings, there is formed a time record of intervals of one one-hundredth of a second. For this purpose there is provided a synchronous motor 41 on whose spindle, or geared to which, there is provided an open disk 42 having a series of ten spokes 43. One of these spokes is broken away in part so as to distinguish it from the others. The disk 42 is revolved by the motor so as to carry the spokes successively across the path of the beam of light before mentioned with the result that light is excluded from the film at the proper intervals and a continuous series of transverse lines is formed. Due to the broken away portion of one spoke, every tenth line will be broken to designate tenths of seconds. In order to insure uniformity in the speed of operation of the synchronous motor, the latter is preferably controlled by means of a tuning fork 44 or similar device having a definite frequency. Thus, when the fork is set in vibration by contacts 400 at are successively made and broken. Contacts 46 merely form part of a circuit through a coil 47 of an electro-magnet which serves to supply new powerto the fork to keep it in The set of contacts on the other hand are in the circuit of the synchronous motor and serve to impose the de sired frequency u on the latter.

location of the sending station A on the opposite side of the point of explosion pinching it, two sets of contacts 45 and 4 6 from that on which the stations B, C, and D, are located, serves to provide data for the area in the immediate vicinity of the point of explosion. It is well known that waves of the character set up will penetrate the earth to a distance of approximately one-sixth of the horizontal distance through which it travels, and waves of this type furthermore follow practically a hyperbolic path. For this reason a wave received at any of the stations will only have passed through an elasti c deposit, such as 24, at any considerable depth about midway betweenthe point of explosion and the terraphone receiving the wave. At a point relatively close to the point of explosion, a refracted, or direct wave will have penetrated to only a relatively short distance so that it is unlikely that any of the stations B, C, or D would indicate a deposit within a few thousand feet, or perhaps a mile of the source and at a depth of five hundred or more feet. However, the terraphones of station A would receive the reflected Waves from such a subterranean body so that the usual dead area immediately surrounding the point of explosion is eliminated.

Referring to Figure 9, which illustrates a small section of a record such as might be formed at one of the receiving stations, the line 50 that string of the oscillograph which may either be affected by the radio apparatus or one of the terraphones while the line 51 represents the record obtained from the remaining string which is affected solely by its related terraphone. The break 52 in line 50 indicates the radio signal sent out upon the closing of the explosion switch 15, while the following break 53 in the opposite direction indicates the opening of this switch. At 54 a sharp break may be observed at the beginning of a series of vibrations of considerable amplitude. This may represent the instant of receipt of thewave caused by the explosion after the wave has traveled down to a considerable depth and has been refracted through a salt dome or similar elastic medium to send it in the direction of the terraphone or other detector. Another sudden break as indicated at 55 may be interpreted as the instant of receipt of the more slowly traveling direct ground wave while still another disturbance beginning at the point 56 may indicate the receipt of a sound Wave through the air. The breaks in the line 50 designated by the numerals 57 and 58 will indicate the beginning and end of a dot, for example, sent out by radio from station A as the beginning of a symbol to identify the particular record with a particular explosion. In somewhat similar fashion the line 51 may be broken at the points 59, 60 and 61 to show the time of receipt by its terraphone of the refracted, direct-ground, and

represents the record obtained from to coincide pretty tially the same.

. record, it willjbe .two separate single string the same or separate record strips.

-plo the two string sue a way that one 'the impulse created upon 5 the the oscillograph are sufliciently uniform in air-sound waves respectively. Due to the system of laying out .the locations of the terraphones with respect to the point of explosion, the breaks and 61 -will be found well with the breaks 55 and 56 in the line 50 since the length of the paths through which the corresponding waves will havetra'yeled will be substan- On';the other hand, the refracted waves picked up by the two detectors ata given st'ationmay have traveled through paths of bite digferent length and character "so that e points 54 and 59 will not necessarily coincide. The same would be true in the case. of reflected waves included in the record. The time lines 62 represent periodic time' intervals of one onehundredth of a second, while the break 63 in every tenth onel of these lines will indicate tenths of seconds. While the foregoing brief discussion of Ei ure 8 will serve to ring out the possibilitles of interpreting the records and the advantage of having the two lines 50 and'5l in close relation on a single clear that a careful study and comparison of all of the records produced at the several stations will reveal many interesting facts concerning t terranean conditions.

Insofar as the present invention is concerned, the specific construction of the various instruments employed is not important so long as the functions prescribed. Suitable devices .are well known which are capable of perfunctions: galvanometer has been referred to as forming forming a all of the necessary While a single two string part of the oscillograph, this may, if desired, be replaced by alvanometers producing photographic records upon either It has been found advantageous, however, toemtype of galvanometer in of the strings may'not only record the vibrations detected by a terraphone but may also record theradio irn-e pulses inthe manner indicated as well as the explosion of charge. If the film feeding devices of h action, it will not be necessary to provide in means although as desirable to this ,mstrument separate time marking it has been found preferable practice to employ such means to mark intervals of one one-hundredth of a second. It has been mention have all of the apparatus ready mounted in a car- 'fonpurposes of transportation and convenient use.

mount the apparatus detachable so that it may be carried into places which may be inaccessible to the car.

While a preferred method of and suitable .the detection of such waves at a plura he subthey are capable of performing 7 said points pendicular of intersection of said At the' same time, it will be found desirable to soas to make it easily.

apparatus for, carrying out the process of surveying the earths surface has been de-.

1. The method of exploring the earths the generation of the surface, and lity of .stations at substantially the same time, somelof said stations being arranged in substantially a straight line and at least one of said stations being arranged at a side of the point where the compressional waves are generated opposite from those stations arranged in a straight line.

2. The method of exploring the earths surface which comprises the generation of compressional waves below the surface, and the detection of such waves at a plurality of stations, at substantially the same time, some of said stations being on opposite sides of the source of said waves, and one of said stations being closer to said source than the remaining stations.

3. The method of exploring the earths surface which comprises the generation of compressional waves below the surface and the detection of such waves at a plurality of stations at substantially the same time, some of said stations being arranged in 51;}:-

e point where the compressional waves are generated, and at least one of being arranged at the side t 'those stations arranged in a straight line and on a line passing through the point for the generation of said waves an substantially perpendicular to said straight line.

' 4. The method of exploring the earths surface which comprises he generationof compressional waves below the surface, detectingsaid waves at a plurality of points at a distance from the source of said waves,

being located along a line perto a line radiating from said at equal distances from the point lines, and producing a single common record of the waves detected at all of said points. 4

5. Apparatus for detecting and recording compressional waves set up in the earths surface includinga lurality of vibration detectors, a' recorder aving separate record controlling elements for each of said detecsurface which comprises compressional waves below source and of said point for neration of said waves opposite to I tors, and means for affecting one of said elements to produce a record at the instant of generation of said waves.

6. Apparatus for detecting and recording compressional waves set up in the earths surface including a plurality of vibration detectors, a recorder having separate record controlling elements .foreach of said detectors, and means for afi'ecting one of said elements to produce a record at the instant of generation of said waves, said means and one of said detectors being in constant effcctive relation with respect to one of said elements.

7. In the method of determining the earths structure by causing an explosion from a control point and recording the characteristics of the waves thus set up and transmitted to a plurality of receiving stations the steps comprising the emission of a radio signal at the control point upon closing an electric circuit to cause the explosion, the recording of said signal at said receiving stations, and the recording at the control point of the instant of closing said circuit as well as of the instant of explosion.

8. In apparatus for examining the earths structure by the use of an explosive charge, electrical means for setting off said charge, said means including a control switch, means for recording at a control point and a plurality of receiving stations the instant of closing said switch, and means for recording at said control point the instant of the explosion.

9. In a method of exploring the earths surface by the generation of compressional waves at one point and the reception of said waves at a plurality of stations, the steps comprising operating a signalling device at said one point and directional signal receiving devices at said stations, adjusting said signal receiving devices to determine their directions with relation to said point, setting up compressional waves, and receiving said waves by detecting devices placed at equal distances on opposite sides of said stations along lines perpendicular to the lines of direction determined.

10. In apparatus for determining earth structure by the study of artificial vibrations, the means for obtaining the relative location of the source and reception points of said vibrations comprising radio transmitters at said source and one of said recep tion points, radio compasses provided with loops at all of said reception points adapted to determine a bearing relative to said transmitters, and a magnetic compass at each of said reception points adapted to determine the positions of the loops of said radio compasses with respect to magnetic north.

11. Apparatus for determining earth structure by the use of compressional waves,

means for generating compressional waves,

means for detecting said waves at a point remote from said generating means, means for recording said detected waves, connections between said detecting means and said recording means, a radio transmitting device automatically operable upon the generation of said compressional waves, a radio receiving device, means controlled by said radio receiving device and including a transformer associated with the connections between said detecting means and said recording means for affecting said recording means to produc a record, and separate key operated means for cont olling said recording means at will.

HARVEY C. HAYES. 

